Apparatus for photometrically scanning gels

ABSTRACT

An apparatus for photometrically scanning gels comprises a monochromator from which the light beam passes through a stop aperture and a gel placed in a cell, which are installed one after the other along the path of the light beam. The cell is caused to move relative to the light beam by means of a drive and the light is received by a photometer. The cell is made in the form of two superposed discs each having on one side congruent grooves which define at least one compartment for placing the gels therein when the discs are superposed on one another.

FIELD OF THE INVENTION

The invention relates to photometric equipment and, more particularly,it deals with apparatus for photometrically scanning gels obtained as aresult of the electrophoretic analysis.

BACKGROUND OF THE INVENTION

The method of electrophoretic analysis of biological preparations ingels is one of the main areas of biochemical, medical and selectionstudies.

The widespread application of the method is due not only to its highresolution, simplicity and low cost of necessary equipment, but also tothe possibility of effecting parallel analysis of a large number(several scores) of biological preparations. This imposes more stringentrequirements on apparatus for photometrically scanning gels, inparticular, on the productivity, cost, compactness and possibility ofensuring high measurement accuracy.

In addition, the trend to improve the method of electrophoretic analysisof biological preparations in gels with the aim of increasing the gellength has recently become obvious as this would enable the achievementof maximum efficiency of the analysis--maximum separation ofpreparations of complicated composition. The development of apparatusfor photometrically scanning such gels which are up to 40-50 cm longrequires the application of radically new technical concepts becauseconventional apparatus used for such purpose would be unwieldy (up to100-120 cm long) which is due, among other things, to considerabledifficulties in providing for uniform translational motion of gelsduring scanning thus resulting in a more complicated design and highercost.

DESCRIPTION OF THE PRIOR ART

Known in the art is an apparatus for photometrically scanning gels,comprising a monochromator from which the light beam passes, through astop aperture and a gel placed in a cell which are installed one afterthe other along the light beam path, the cell being caused to moverelative to the light beam by means of a manual drive having amicrometric gearing, and the light being received by a photometer (cf.G. Maurer. Disc-Electrophoresis (in Russian), 1971, MIR PublishingHouse, Moscow, pp.103-104, FIG. 29).

In this apparatus, the cell is made in the form of a quartz tube of aconstant diameter which is caused to reciprocate by means of a manualdrive.

As the quartz tube in this apparatus is 7 cm long, only one gel may beplaced in the tube. This requires frequent recharging of the cell, hencethe productivity is low.

The use of expensive quartz tubes in the apparatus makes it rathercostly. For photometrically scanning gels of different diameters, it isnecessary to have a set of quartz tubes of respective diameters whichconsiderably raises the cost of such an apparatus. In case a singlequartz tube is used for studying gels of different diameters,deformation of gels when placed in the tube or a loose accommodation ofthe gel in the tube make errors in scanning more likely.

In addition, the use of the manual drive for moving the cell in thisapparatus results in a low productivity in scanning gels and in highprobability of errors in performing multiple repeated operations ofmoving the cell through one and the same distance read from themicrometric vernier.

An apparatus for photometrically scanning gels has been proposed,comprising a monochromator from which the light beam passes through astop aperture and a gel placed in a cell which are installed one afterthe other on the light beam path, the cell being caused to move relativeto the light beam by an electromechanical drive and the light beingreceived by a photometer (cf. Booklet ISCo (instruments SpecialitiesCompany), USA, Lincoln, Neb., "instruments with a difference", pp.20-21,May, 1979).

In this apparatus, the cell comprises a quartz tube 25 cm long installedfor reciprocations relative to the light beam under the action of anelectromechanical drive.

The use of the quartz tube 25 cm long, which makes it possible to scantwo gels 12 cm long without recharging, and the provision of theelectromechanical drive enable a higher productivity and smallerprobability of error in scanning gels, compared to the abovedescribedapparatus. But the increase in the productivity is yet insufficient formass-scale analysis operations. Further increase in the cell lengthcannot bring a solution to the problem since this is associated withproblems of the manufacture and operation of rather long quartz tubeswhich should exhibit uniform optical properties over the whole length.An additional difficulty in improving this apparatus, which is alsoassociated with the cell being made in the form of the quartz tube, isthe complicated design of the reciprocatory drive for moving a very longcell. Moreover, the use of expensive quartz tubes as the cells does notpermit lowering the cost of the apparatus of this type.

A large length of quartz tube in this apparatus makes the reciprocatorydrive very complicated, thus resulting in a rather sophisticated designof the apparatus as a whole.

The apparaatus is also large in size as for an accurate movement of thecell 25 cm long the apparatus is provided with a reciprocatory drivewhich is 50 cm long. In conducting biochemical and medical tests, thecompactness of such apparatus is very important as a large number of theapparatus are used even for only one type of analysis.

As distinguished from the abovedescribed apparatus, this apparatus makesit possible to scan both cylindrical and prismatic gels. However, as thecells in this apparatus are of predetermined dimensions, the range ofcross-sectional dimensions of the gels is restricted which makes itdifficult to use the apparatus for scanning electrophoretic patternsobtained in various types of electrophoretic analysis. This results inlimited operational capabilities of the apparatus which is now becominga great disadvantage in analytical studies using gels.

In this apparatus, similarly to that described above, a strong diffusionof light by the cylindrical surfaces of the gels and cell cannot beeliminated. In addition, damage to the gel surface is recorded as afalse peak. This results in the absence of improvement of themeasurement accuracy in this apparatus compared to the abovedescribedapparatus, the errors being associated with the negative influence oflight diffusion and surface damages to the gel on the scanning results.

In both abovedescribed apparatus errors associated with nonuniformposition of gels or their loose accommodation in the cell cannot beeliminated.

SUMMARY OF THE INVENTION

The invention is based on providing a simple and compact apparatus forphotometrically scanning gels, in which the cell for the accommodationof gels is made in such a manner as to provide for a substantialimprovement of the gel scanning productivity and measurement accuracy,to lower the cost and to improve the operational capabilities of theapparatus.

This is achieved by an apparatus for photometrically scanning gels,comprising a monochromator from which the light beam passes through astop aperture and a gel placed in a cell, which are installed one afterthe other along the light beam path. The cell is caused to move underthe action of an electromechanical drive and the light is received by aphotometer. According to the invention, the cell comprises twosuperposed discs each having on at least one side thereof congruentgrooves which define at least one compartment for placing gel thereinwhen the discs are superposed on one another.

Apertures are preferably made in both discs of the cell on the groovebottom side for the passage of the light beam.

This construction of the apparatus according to the invention makes itpossible to improve the productivity of scanning owing to the reductionof the total number of auxiliary operations associated with charging thecell with gels and with installation of the cell in the apparatus.Placing several gels into the cell makes it possible to conduct scanningfor a longer time period during which the operator may attend to otheroperations. The time for placing several (e.g., four) gels in theapparatus according to the invention is substantially equal to the timeneeded for placing one gel in the abovedescribed prior art apparatus.

In addition, the provision of the cell in the form of two discs havingcongruent grooves makes it possible to improve the accuracy ofmeasurement owing to the possibility of uniform accommodation of gels inthe cell provided by the design of the cell thus preventing axialdeformation of gels, and an exactly reproducible position of the gelsduring scanning is ensured. For this reason, scanning gels in theapparatus according to the invention enables high reproducibility ofresults and an accuracy which is constant for all measurements. This isvery important as it is crucial for the gel analyses to have thepossibility of quantitative comparison.

In addition, this construction of the cell makes it possible to avoidthe need for using quartz tubes, thus lowering the cost of theapparatus.

A substantial increase in the working length of the cell compartmentsdefined by congruent grooves in the cell discs makes it possible to scangels of a large length thus considerably improving the operationalcapabilities of the apparatus. Moreover, the capabilities of theapparatus are also improved by the cell being made in the form of twodiscs having congruent grooves. This facility makes it possible to scangels of different diameters, so that the apparatus may be used forscanning electrophoretic patterns obtained as a result of various typesof electrophoretic analysis in gels.

The structural embodiment of the cell according to the invention enablesa substantial reduction of the size of the apparatus for scanning gels,whereby the cell dimension which determines the size of the apparatus asa whole is three times as small as the working length of the cellcompartment.

In case grooves are made on either side of each disc of the cell in theapparatus according to the invention, the grooves made on the other sideof the discs may function as the apertures for the passage of light,and, when the discs are superposed on each other with these sides facingtoward one another, they also may define at least one compartment forplacing gel therein.

This embodiment makes it possible to improve the operationalcapabilities of the apparatus, namely, to scan gels having a differentcross-sectional configuration, e.g., rectangular configuration.

The provision of this capability in the apparatus according to theinvention is very important as electrophoretic analysis in gel plateshas recently come into a widespread use. In such case, the scanning isconducted after cutting individual electrophoretic samples from theplate.

The grooves of the cell discs are preferably made along the perimeter ofeach disc.

This embodiment of the cell makes it possible to substantially simplifythe apparatus since a simple and cheap electromechanical drive may beused for causing the cell to move relative to the light beam from themonochromator.

The apparatus is preferably provided with a bath filled with a liquidhaving a refractive index similar to that of the gel material, the bathhaving optically transparent inlet and outlet windows for the light beamand being installed between the stop aperture and the photometer in sucha manner that the part of the cell discs having compartments for placinggels therein should be submerged in the bath liquid.

This facility makes it possible to substantially reduce the lightdiffusion and influence of surface damages to gels on the scanningresults. As a consequence of this, the apparatus according to theinvention has an improved sensitivity in measurements as a result of alower background of light diffusion, and the amplitude of false peaks inthe scanning record caused by surface damages to gels is substantiallylowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail with reference to specificembodiments illustrated in the accompanying drawings, in which:

FIG. 1 is an elevational view, partially in longitudinal section, of anapparatus for photometrically scanning gels according to the invention;

FIG. 2 is a plan view of the inside surface of one of the discs of acall of the apparatus shown in FIG. 1;

FIG. 3 is a view taken in the direction of arrow A in FIG. 1 showing abath with a liquid in which is submerged a part of the cell discs of theapparatus of FIG. 1;

FIG. 4 is a longitudinal section of a part of the cell discs of anotherembodiment of the apparatus according to the invention; and

FIG. 5 is the same as FIG. 4, but with the discs superposed on oneanother with their opposite sides.

DETAILED DESCRIPTION OF THE INVENTION

An apparatus for photometrically scanning gels according to theinvention comprises a monochromator 1 (FIG. 1) from which the light beampasses through a stop aperture 2, an inlet optically transparent window3 of a bath 4 filled with a liquid 5, a gel 6 placed in a cell 7, and anoutlet optically transparent window 8 of the bath 4, which are disposedone after the other along the path of the light beam, the light beingreceived by a photometer 9.

The cell 7 is made in form of two superposed discs 10, 11 made of ametal, e.g., of an aluminium alloy, which have on their inside surfaces12 (FIG. 2) congruent grooves 13.

The grooves 13 of the discs 10, 11 are made along the perimeter of thediscs.

Various embodiments of the apparatus may be used with several groovesdifferently spaced from the center of the discs or even with a singlespiral groove.

When the discs 10 and 11 (FIG. 1) are superposed on one another, thegrooves 13 (FIG. 2) define a compartment 14 (FIG. 1) for placing gels 6therein. In this embodiment of the apparatus a single compartment 14 isdefined in which four gels 6 are placed.

The apparatus may be made with the discs having several compartments.

Both discs 10, 11 have, on the side of the bottom of the grooves 13(FIG. 2), apertures 15 and 16, respectively, for the passage of thelight beam (FIG. 1). Bridges 17 are provided for the discs 10, 11 toremain integral.

Discs 10, 11 (FIG. 1) of the cell 7 are installed on an output shaft 18of a drive 19 for rotation (movement) relative to the light beam.

By using washers of various thickness (not shown) placed between the twodiscs 10, 11 of the cell 7, the space between the discs 10 and 11 may bevaried so as to change the cross-sectional dimensions of the compartment14 thus making it possible to scan gels 6 over a wide range of theircross-sectional size.

As mentioned above, the bath 4 is filled with the liquid 5. The liquidis chosen so that its refractivity index should be similar to therefractivity index of the material of the gels 6. Thus, in thisembodiment the liquid 5 is water as polyacrylamide or agar gels 6 are tobe studied.

The bath 4 is installed between the stop aperture 2 and the photometer 9in such a manner that the part of the discs 10, 11 of the cell 7 (FIG.3) having the compartment 14 (FIG. 1) for placing the gels 6 is in theliquid 5.

As it can be seen in FIG. 3, the bath 4 is in the form of a segment.This is determined by the configuration of the cell 7 and enables savingof the liquid when the liquid might contain expensive additives.

The stop aperture 2 (FIG. 1), the bath 4 and the cell 7 are accommodatedin a housing 20 which has a removable light-protective hood 21. The hood21 has an opening for the output shaft 18 of the drive 19 on which areremovably installed the discs 10, 11 of the cell 7.

The output of the photometer 9 is electrically coupled to a recorder 22having a chart sheet on which is recorded a scanning record 23 havingpeak which are used to assess the position of studied substances in theelectrophoretic sample.

The embodiment of the apparatus according to the invention which hasbeen described above, in which the compartment 14 defined by the grooves13 upon superposing the discs 10 and 11 of the cell 7 on one another, isdesigned for scanning cylindrical gels 6.

However, by changing the configuration of the grooves, gels of differentconfiguration may be scanned.

FIGS. 4 and 5 show the cell 7 of the apparatus according to theinvention which is formed by superposing discs 24 and 25 havingcongruent grooves 26 and 27 on both one side 28 and an opposite side 29,respectively. This construction of the cell 7 enables its applicationfor gels of different configurations.

Thus, in case the discs 24 and 25 of the cell 7 (FIG. 4) are superposedwith their sides 28 facing toward one another, the grooves 26 define acompartment 30 for placing therein cylindrical gels 6, and the grooves27 made on the outer side 29 of the discs 24, 25 function as aperturesfor the passage of light.

When the discs 24, 25 of the cell 7 (FIG. 5) are superposed with theirsides 29 facing toward one another, the grooves 27 form a compartment 31for placing therein gels 32 of a rectangular cross-sectionalconfiguration, and the grooves 26 on the outer side 28 of the discs 24,25 function as apertures for the passage of light.

There may be several commpartments 31 and 32 (FIG. 4).

The apparatus for photometrically scanning gels according to theinvention functions in the following manner.

After the removal of the light-protecting hood 21 (FIG. 1), both discs10, 11 or both discs 24, 25 (FIG. 4) of the cell 7 (FIG. 1) are removedfrom the shaft 18 of the drive 19. The gels 6 or 32 are placed into thegroove 13 or 26 (FIG. 4) or 27 (FIG. 5) of one of the discs 10 or 24 sothat spaces of at least two-three millimeters should be left between theends of the gels 6 and 32 and the bridges 17. Then the disc 11 or 25 issuperposed so that both grooves 13, 26, 27 define the compartment 14, 30for cylindrical gels 6 and compartment 31 for gels 32 of rectangularcross-sectional configuration, and that the bridges 17 of both discs 10,11 or 24, 25 should be brought in register.

Water is poured into the bath 4 (FIG. 1) so that the water level shouldbe slightly above the windows 3, 8. The assembled cell 7 with the gels 6or 32 placed therein is put on the shaft 18 of the drive 19 so that thelight beam from the monochromator 1 should be targeted to the aperture15. Then the light-protecting hood 21 is installed, and the referenceline of the photometer 9 is set-up. The drive 19 is turned on, a well asthe chart sheet transport drive of the recorder 22, and the photometricscanning of the gels 6 or 32 is conducted. The light beam from themonochromator 1 (FIG. 1) passes through the stop aperture 2 whichcuts-out from the beam a narrow beam 0.2 mm wide passing, consecutively,through the inlet window 3 of the bath 4, the water, the aperture 15,the gel 6, the aperture 16, the water, the outlet window 8 of the bath 4and is incident upon the photometer 9. The absorption of the light beampassing through the gel 6 is recorded by the recorder 22. The points oflocation of the zones of the biological substance being analyzed in thegels are recorded by the recorder as peaks on the scanning record 23.After the discs of the cell 7 have performed a complete revolution, thescanning process is terminated. Scanning the gel 32 (FIG. 5) of therectangular cross-sectional configuration is performed in the similarmanner.

For placing into the cell gels of a size greater than thecross-sectional size of the compartment, washers of a thicknesssufficient for fixing the gels are placed between the discs.

In a specific application of the apparatus according to the invention, aconsecutive scanning of four, e.g., cylindrical gels each 12 cm long orone gel 50 cm long is possible without recharging the cell. The groovesin the discs of the cell are made with a 17 cm diameter. As the width ofthe light beam passing through the gel during the scanning is normallybetween 0.1 and 0.5 mm, the curvature of the gels along an arc of 17 cmin diameter does not affect the accuracy of measurement.

The application of the apparatus according to the invention makes itpossible, the other conditions being equal, to improve the accuracy ofscanning gels by 1.5-2 times, to obtain a 3-4-fold reduction of thenumber of auxiliary operations and to lower the cost of the apparatus bya quarter.

INDUSTRIAL APPLICABILITY

The apparatus for photometrically scanning gels according to theinvention may be used in clinics and at microbiological factories forconducting mass-scale tests with the quantitative evaluation ofelectrophoretic patterns in gels, e.g., in polyacrylamide and agar gels,as well as for conducting selective operations in agriculture.

I claim:
 1. An apparatus for photometrically scanning gels, comprising amonochromator from which a light beam pases through a stop aperture anda gel placed in a cell, which are installed one after the other alongthe path of the light beam, the cell being caused to move relative tothe light beam by means of an electromechanical drive and the lightbeing received by a photometer, wherein the improvement comprises thecell comprising two superposed discs each having on at least one sidethereof congruent grooves which define at least one compartment forplacing gels therein when the discs are superposed on one another.
 2. Anapparatus according to claim 1, wherein both discs of the cell haveapertures in a surface opposite to the surface in which the groove isdefined and in line with the bottom of the grooves for the passage oflight.
 3. An apparatus according to claim 2, wherein grooves are made onboth sides of the discs of the cell, the grooves made on the oppositeside of the discs of the cell function as apertures for the passage oflight, and, when the discs are superposed on one another with thesesides facing toward one another, they also define at least onecompartment for placing gels.
 4. An apparatus according to claim 1wherein the grooves of the discs of the cell are made along theperimeter of the discs.
 5. An apparatus according to any claim 1 through4, further comprising a bath filled with a liquid having a refractivityindex similar to the refractivity index of the material of the gels, thebath having an optically transparent inlet window and an outlet windowfor the passage of light beam and being installed between the stopaperture and the photometer, the part of the discs of the cell havingthe compartment for placing the gels therein being submerged in the bathliquid.